Boron nitride microribbons strengthened and toughened alumina composite ceramics with excellent mechanical, dielectric, and thermal conductivity properties
Jilin Wang, Dongping Lu, Weiping Xuan, Yuchun Ji, Ruiqi Chen, Shaofei Li, Wenbiao Li, Wenzhuo Chen, Shilin Tang, Guoyuan Zheng, Fei Long
Abstract
Aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) ceramics have been widely utilized as circuit substrates owing to their exceptional performance. In this study, boron nitride microribbon (BNMR)/Al<sub>2</sub>O<sub>3</sub> composite ceramics are prepared using spark plasma sintering (SPS). This study examines the effect of varying the amount of toughened phase BNMR on the density, mechanical properties, dielectric constant, and thermal conductivity of BNMR/Al<sub>2</sub>O<sub>3</sub> composite ceramics while also exploring the mechanisms behind the toughening and increased thermal conductivity of the fabricated ceramics. The results showed that for a BNMR content of 5 wt%, BNMR/Al<sub>2</sub>O<sub>3</sub> composite ceramics displayed more enhanced characteristics than pure Al<sub>2</sub>O<sub>3</sub> ceramics. In particular, the relative density, hardness, fracture toughness, and bending strength were 99.95%±0.025%, 34.11±1.5 GPa, 5.42±0.21 MPa·m<sup>1/2</sup>, and 375±2.5 MPa, respectively. These values represent increases of 0.76%, 70%, 35%, and 25%, respectively, compared with the corresponding values for pure Al<sub>2</sub>O<sub>3</sub> ceramics. Furthermore, during the SPS process, BNMRs are subjected to high temperatures and pressures, resulting in the bending and deformation of the Al<sub>2</sub>O<sub>3</sub> matrix; this leads to the formation of special thermal pathways within it. The dielectric constant of the composite ceramics decreased by 25.6%, whereas the thermal conductivity increased by 45.6% compared with that of the pure Al<sub>2</sub>O<sub>3</sub> ceramics. The results of this study provide valuable insights into ways of enhancing the performance of Al<sub>2</sub>O<sub>3</sub>-based ceramic substrates by incorporating novel BNMRs as a second phase. These improvements are significant for potential applications in circuit substrates and related fields that require high-performance materials with improved mechanical properties and thermal conductivities.